1. Field of the Invention
The present invention relates to a radio communication apparatus and, more particularly, to a small-sized radio communication card which can be detachably attached to various portable electronic apparatuses.
2. Description of the Related Art
Recently, memory cards smaller than PC cards have been developed for mobile apparatuses such as a PDA, camera, portable telephone, and audio player. An SD (Secure Digital) memory card of postage stamp size is known as a representative small-sized memory card.
Since the thickness of this SD memory card is only about 2 mm, no card edge type connector such as that of a PC card is used. Instead, electrodes functioning as signal pins are exposed from the surface of a card substrate and are used as a connector unit.
The number of signal pins of this connector unit is 9, four of which are used as data pins. That is, an SD memory card improves the data transfer rate by realizing 4-bit data transfer, compared to conventional small-sized memory cards which perform 1-bit data transfer.
In recent years, even such small-sized card media are beginning to be required to have functions as IO devices such as a modem card and network card. For example, by realizing an IO card (to be referred to as an SD IO card hereinafter) having the same shape as an SD memory card, it is possible to achieve effects such as: 1) an SD memory card and an SD IO card can be attached to the same card slot, and 2) the functions of even a small-sized electronic apparatus, on which a connector for connecting various I/O devices is difficult to mount, can be readily extended.
Lately, radio communication standards represented by Bluetooth for connecting diverse electronic apparatuses by radio have been layed down. If such radio communication functions are realized as an SD IO card, these radio communication functions can be easily installed in mobile apparatuses, such as a PDA, camera, portable telephone, and audio player, having an SD memory card slot.
As described above, however, an SD IO card is a thin, small-sized card of postage stamp size and is assumed to be used in a mobile apparatus. To install radio communication functions, therefore, it is important to simplify and downsize the internal arrangement of a card and to reduce the cost. Furthermore, since a mobile apparatus is a host, it is necessary to reduce the load on the host and well consider the mounting position of an antenna and the power-saving properties.